Stuffing boxes are typically define a circulation passage of a cable working line extending between an upstream end of the stuffing box, intended to be connected to the well, and a downstream end. The stuffing box usually includes at least one packer arranged in the passage to ensure the sealing between an upstream portion and a downstream portion of the passage when the line is inserted in the passage. The stuffing box further includes a back-pressure resistant valve arranged in the passage to prevent, in case of break of the line, the back-pressure of a fluid from the upstream end towards the downstream end. Such a stuffing box is generally part of pressure control equipment, intended to be mounted on the wellhead. The pressure control equipment thus generally comprise, from bottom to top, a device for preventing back-pressure of the fluid contained in the well (designated by the term “Blow Off Preventer,” or BOP), a lock, and the stuffing box.
The aforementioned equipment ensures the safe passage of operating tools deployed in the well by a cable working line between the atmospheric pressure reigning outside the well and the internal pressure of the well when an operation is necessary in the well. Such control equipment is used for fluid production wells, such as hydrocarbon production wells such as oil or natural gas, or for injector wells. It is essential to ensure the surface safety of operations in the well. The lock allows objects to be introduced in the well. The stuffing box is arranged above the lock to ensure sealing around the cable working line, and orient the cable working line in the well with the aid of a return pulley.
The stuffing box comprises a hollow vertical body through which the cable working line passes and which ensures the sealing between the upper part of the lock, subjected to the pressure from the well, and the outside subject to the atmospheric pressure. To that end, the sealing is done by annular rubber packer elements that are annularly applied around the cable, between a fixed lower stop and an adjustable upper stop, adjustable for example using a piston. To unwind the cable working line, it is known to use a drawworks, which is brought near the well and maneuvered in rotation to wind or unwind the line in the well.
The cable working lines generally used in particular include single-strand smooth cables, of the “piano wire” or “slickline” type. These lines make it possible to perform various mechanical operations (commonly called “cable operations”) at the bottom of the well, such as opening and closing valves, placing elements or tools, or perforating a wall. The cable working lines used can also be electrically insulated cables, of the “Gemline” type.
It does, however, happen that the cable working line breaks and completely leaves the stuffing box. The stuffing box no longer ensures sealing and there is then a risk of fluid discharge from the well into the environment. In order to prevent such a discharge, stuffing boxes are generally equipped with a back-pressure resistant valve.
In the known stuffing boxes, the back-pressure resistant valve is generally situated between the packer elements and the end of the stuffing box connected to the well. This results in crushing of the valve, which sometimes prevents it from performing its function.
On the other hand, in the known stuffing boxes, the back-pressure resistant valve is generally a ball valve. The valve defines a housing in which the ball rests during normal time. A pipe emerges in the bottom of said housing and in the circulation passage of the cable working line.
Thus, when the cable working line breaks, the pressure increases in the passage under the effect of the fluid coming from the well. This pressure increase is passed on at the bottom of the housing through the pipe, which causes the ball to be ejected outside the housing. The ball then obstructs the passage, thereby ensuring sealing between the upper part of the lock and the atmospheric pressure.
Such a device is not, however, fully satisfactory. Indeed, the pipe forms a dead space in which impurities are deposited. It thus occurs that impurities block the pipe, which blocks the operation of the valve.
One aim of the disclosure is therefore to propose a stuffing box with a more reliable operation than the known stuffing boxes.